1. Field of the Invention
The present invention relates to systems and methods for the transmission of video and related information, and in particular to a system and method for transmitting and receiving auxiliary data at a plurality of selectable clock speeds as a part of a high definition video signal.
2. Description of the Related Art
Standard analog color TV broadcasting techniques developed over 50 years ago have allowed the design of inexpensive television receivers that can provide remarkably good picture quality. Nonetheless, recent advances in transmission bandwidth and compression techniques have aroused considerable interest in high definition television (HDTV). HDTV, which is currently available on a limited basis in selected media markets, offers much higher picture quality than ordinary television sets.
Standard television receivers use an interleaved scanning technique that provides for horizontal blanking intervals between lines and vertical blanking intervals between each field of the interleaved picture frame. Standard television sets are capable of broadcasting auxiliary information associated with the television program by transmitting the information during the vertical blanking interval of the scanning television signal. Specially equipped television receivers can receive this information and provide it to the viewer. In the past, this technique has been used to provide low bandwidth information.
DTV is capable of delivering auxiliary data at a much higher rate than was possible with conventional television broadcasts.
FIG. 1 is a block diagram illustrating a system 100 for transmitting and receiving a digital television (DTV) signal comprising video, audio, and auxiliary information. Data packetization techniques are used to combine video, audio, and auxiliary information for each of a multiple of program streams into a single digital transport stream. The transport stream is suitably modulated and transmitted to a program receiver 110 or set top box. The program receiver 110 receives the modulated signal, and separates the video, audio, and auxiliary data into its component parts. Each component part is then routed to the appropriate devices. The program receiver 110 may also receive the video, audio, and auxiliary information via component interfaces.
As shown in FIG. 1, one or more video signals are provided from a program provider 102 to a program receiver 110 via satellite 104 or terrestrial transmitter 106 broadcast or cable/internet 108 to a program receiver 110 and thence provided to one or more inputs 112, 114, 116, 118 and 120 to one or more presentation devices 122, 124 and 126. Inputs 112, 114, 116, 118 and 120 may also be provided to a recording/playback device 128, which can record the input signals 112, 114, 116, 118 and 120 and provide the recorded input signals 112, 114, 116, 118 and 120 when required.
Inputs 112, 114, 116, 118 and 120 include a plurality of video component signals. These include audio signal(s) 112, and various video signals including a luminance signal 114, a first color signal 116 (typically, hue), a second color signal 118 (typically, intensity) and auxiliary data signal(s) 120.
As is well known and as previously noted, DTV signals are typically broadcast as digital bitstreams, typically utilizing a time division multiplex packet stream. In such systems the video component signals are encoded as digital information utilizing suitable protocols, and included in the broadcast bitstream. In some known devices the video (and/or audio) information is output from the program receiver 110 to the video presentation device 124 in a digital format. For example, the National Cable Television Association (NCTA) has recently proposed standards for utilizing an IEEE 1394 serial interconnect for connecting cable receiver boxes to ATSC compatible display devices. In such a system, the video information is communicated in packetized digital format and interpreted within the television receiver as needed (e.g. utilizing an MPEG-2 decoder). There are both advantages and disadvantages to digital interconnects of this type as compared to interconnects utilizing analog signals to communicate the video information. Due to its digital nature, it is straightforward to include auxiliary data within the communicated bitstream, including locally-generated data. Further, there are known techniques for securing the communication between devices using digital technology, such as encryption techniques (e.g. the DTCP-5C technology proposed for use with IEEE 1394). However, known affordable digital interconnect systems have bandwidth limitations that limit their desirability for communicating certain forms of video information. By way of example, a typical uncompressed digital HDTV video signal requires a bandwidth which exceeds the capability of the IEEE 1394 interconnect.
Because of these and other limitations, it is often desirable to use an analog interconnect utilizing analog waveforms representing the various video (and optionally, audio) information. Video component signals can be embodied in a number of different known or alternative analog forms, such as red, green, and blue (RGB) components, or luminance, scaled red-luminance, and scaled blue-luminance signals (Y, Pr, and Pb) component signals among others. Such analog video signals typically incorporate blanking intervals analogous to those defined in the NTSC standards, including vertical blanking intervals (VBI). In a system wherein the broadcasts are in digital format, the program receiver 110 includes circuits for generating the analog video waveforms and for structuring the respective outputs in a format having blanking intervals including VBI. By way of example and referring again to FIG. 1, the analog signals utilized for interconnecting a receiver 110 to a presentation device 124 in a typical HDTV system might include audio signal(s) 112 in either analog (e.g. FM) or digital (e.g. MPEG or AC-3) format, an analog luminance signal 114, an analog first color signal 116, an analog second color signal 118, and auxiliary data 120. Each of the video signals 114, 116 and 118 typically include a VBI, and some or all of the auxiliary data 120 can be communicated by use of one or more of these VBIs.
While the systems described above allow the transmission of auxiliary data to the video presentation device 124 for display (i.e. closed captioning) or to other devices for other use (i.e. copy protection), the sub-systems necessary to receive and decode the auxiliary data signals in the video presentation device 124 are not inexpensive. Further, the cost of these subsystems typically increases as the bandwidth of the auxiliary data increases. For example, more complex circuitry is required to receive and decode data at higher clock speeds. Since some viewers may require higher bandwidth auxiliary data services, and some may not, this can result in unnecessarily expensive video devices (e.g. video presentation devices 124) for most consumers, or the inability to transmit auxiliary data having higher bandwidth requirements to any users at all. What is needed is a system that provides for secure transmission of auxiliary data information of different data rates to a wide variety video devices. The present invention satisfies that need.
To address the requirements described above, the present invention discloses a method, apparatus, article of manufacture for generating a video signal having an auxiliary data payload complying with a data payload protocol selectable from at least two available and differing data payload protocols.
An exemplary embodiment of the method comprises the steps of generating a data reference signal (which describes an auxiliary data payload protocol including an auxiliary data payload clock speed) at a baseline clock speed compliant with both of the two data protocols; appending the auxiliary data payload signal at the auxiliary data payload clock speed to the data reference signal; and inserting the data reference signal and the appended auxiliary data payload signal in a portion of at least one line of a video frame. An exemplary embodiment of the apparatus comprises a generator, for generating at least one line of a video frame having a data reference signal at a baseline clock speed compliant with two data protocols and an appended auxiliary data payload. The data reference signal is compliant with the two data protocols and describes a selected auxiliary data payload protocol including the auxiliary data payload clock speed.